This invention relates to acoustic damping material. More particularly, this invention relates to acoustic damping material for use in various acoustic devices, such as acoustic speaker systems and acoustic damping panels.
Acoustic speaker systems generally include at least one acoustic speaker mounted to a speaker enclosure. The speaker converts electric energy into acoustic energy over a particular frequency range. The conversion of electric energy into acoustic energy is limited by the mechanical constraints of the speaker and its enclosure. For example, in conventional electromagnetic speakers, an electric current energizes an electromagnet that is fixed to a lightweight flexible surface, producing an electromagnetic field. This field interacts with another magnetic field produced by a permanent magnet fixed to a frame holding the flexible surface. During operation, the interaction between the fields produces a force which drives the surface to vibrate at the frequency of the electric signal, thereby producing acoustic energy.
An important disadvantage of acoustic speaker system enclosures is the large physical size required to ensure a balanced and efficient low frequency response. The primary reason for using a large enclosure is to provide a sufficient volume of air against which a woofer can freely vibrate. Small enclosures, however, contain small volumes of air which restrict the vibratory motion of the woofer. Acoustic dampening materials such as fiberglass, wool, and synthetic polyester fibers (such as those sold under the trademark DACRON.RTM., by E. I. du Pont de Nemours & Company, of Wilmington, Del.), are often used to diminish the enclosure size requirement. Unfortunately, however, because of these materials' low acoustic absorption, the use of these materials can not substantially reduce the size of the enclosure and simultaneously ensure a balanced low frequency response.
Furthermore, because conventional acoustic damping materials do not efficiently absorb the acoustic energy during speaker operation, the enclosure absorbs it, and subsequently releases it in the form of acoustic energy at different undesired frequencies, including, possibly, undesirable harmonics of desirable acoustic frequencies.
Acoustic damping materials can also be useful for absorbing sound in substantially enclosed spaces, such as sound recording rooms and areas that are subject to undesirable noise. One method for absorbing sound includes mounting acoustic damping panels on one or more walls of the enclosed space. However, a disadvantage of conventional acoustic damping materials, which are often made from foamed materials, is that such materials are generally expensive and relatively inefficient.
It would therefore be desirable to be able to provide an acoustic damping material that can be used whenever acoustic energy is desirably absorbed.
It would also be desirable to provide an acoustic speaker system that is physically small and produces a broad balanced response over the entire audible spectrum, especially at low frequencies.
It would further be desirable to be able to provide an acoustic damping material that efficiently absorbs acoustic energy for improving the accuracy of the acoustic reproduction of electric signals of an acoustic speaker system.
It would be even further desirable to be able to provide an inexpensive, yet highly efficient, acoustic damping panel for absorbing acoustic energy in substantially enclosed spaces.